The present invention generally relates to a sheet separating apparatus and more particularly, to a sheet separating arrangement used for smoothly transporting sheets, e.g., paper sheets such as original documents containing various information, sheets for recording and reproducing, etc. piled up in a stack, towards a reading section or recording and reproducing section through separation sheet by sheet, in such appliances as a facsimile apparatus, copying apparatus, optical character reading device, or the like.
Conventionally, a known sheet separating arrangement used for the purpose as described above generally has the construction as shown in FIG. 1, and includes a transport path 3 defined between a lower sheet guide plate 1 and an upper sheet guide plate 2 for guiding sheets, for example, paper sheets such as original documents, etc., a pay-out roller 4, a depressing member 5 held in pressure contact with the pay-out roller 4, a sheet feeding roller 6, a transport roller 7 and a pinch roller 8 held in pressure contact with the transport roller 7, which are sequentially disposed along the transport path 3 from the upstream side in the transport direction, as illustrated.
The depressing member 5 referred to above and pivotally connected to a frame (not shown) by a shaft 9, is held in pressure contact with the pay-out roller 4 by an urging force of a depressing spring 10 connected between the depressing member 5 and the upper sheet guide plate 2, and is prevented from further rotation by the contact of a stopper 11 projecting therefrom, with the corresponding surface of the upper sheet guide plate 2.
In a position above the sheet feeding roller 6, there is provided a sheet separating unit 12 which separates sheets for feeding one sheet at a time. The sheet separating unit 12 includes a separating member 12b having an L-shaped cross section and pivotally connected to the frame by a shaft 12a so as to be inclined in the sheet feeding direction, a separating plate 12c of rubber or rubber-like material superior in abrasion resistance and fixed to the under surface of the separating member 12b, and a compression coil spring 12e disposed between an angle member 12d sescured to the upper sheet guide plate 2 and the separating member 12b for urging the separating member 12b toward the sheet feeding roller 6 so as to keep the separating rubber sheet 12c in pressure contact with the roller 6 under a predetermined pressure, thereby to effect the function of separating the sheets as fed, into individual sheets. Moreover, since it is difficult to separate a large number of sheets stacked on a hopper 13 into individual sheets only by the sheet separating unit 12, there is provided a sheet stopper member 14 on the upper sheet guide plate 2 at a position close to the contacting point between the pay-out roller 4 and the depressing member 5 so as to be inclined toward the sheet feeding direction and also spaced from the surface of the lower sheet guide plate 1 by a predetermined distance, and thus, movement of the sheets is restricted by this sheet stopper member 14 so that more sheets than necessary are not fed to the sheet separating unit 12.
However, in the sheet separating unit 12 as described above, since the urging of the separating rubber plate 12c toward the sheet feeding roller 6 is to be effected by the compression coil spring 12e, it is necessary to forcibly fit the coil spring 12e in between the separating member 12b and the angle member 12d, thus resulting in low efficiency during assembly work. Moreover, due to the complicated structure for supporting the separating member 12b by the shaft 12a mounted on the frame for merely bringing the separating rubber plate 12c into pressure contact with the sheet feeding roller 6, the number of parts is undesirably increased, with a corresponding increase in cost.
Furthermore, since the urging pressure toward the separating rubber plate 12c as determined by the spring constant of the coil spring 12e can not be adjusted, in cases where any trouble such as faulty sheet feeding or the like arising from the pressure of the separating rubber plate 12c should take place during operation by users, it becomes necessary to replace the coil spring with another one having a different spring constant.